Thin film transistors have been widely used in display applications such as liquid crystal displays (LCD), electronic paper displays (EPD), and organic light emitting diode displays (OLED).
Generally, a thin film transistor structure includes a substrate, a gate electrode, a gate insulator layer, a channel island, a source electrode, and a drain electrode. The gate electrode is disposed on the substrate, the gate insulator layer covers the gate electrode, the channel island is disposed on the gate insulator layer and the source electrode and the drain electrode are disposed on the channel island.
The above-described type of thin film transistor can be well used in a LCD. However, if the thin film transistor structure is used in an EPD, the channel island might become conductive after being irradiated by external light, resulting in current leakage occurring in the island structure. As a result of the current leakage, the EPD suffers from abnormal displaying (e.g. image or color distortion).
Therefore, how to avoid abnormal displaying and improve displaying quality of EPDs become the area that researchers and developers are focused on.